Attachment interface for connecting a vehicle composite component

ABSTRACT

An attachment interface is provided for connecting a vehicle composite component having a plate portion that is made of a fiber reinforced polymer and has a passage extending in a through manner along an axis. The attachment interface provides a metal attachment device, which includes an inner portion engaging the passage and an outer portion defining a connection point suitable to be connected to another vehicle element. The plate portion is axially sandwiched between two layers made of a fiber reinforced polymer composite material selected from the group consisting of BMC (Bulk Molding Compound), LFT (Long Fiber Thermoplastic) and DLFT (Direct Long Fiber Thermoplastic).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Italian patent application no.102018000007977 filed on Aug. 8, 2018, the contents of which are fullyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention concerns an attachment interface for connecting avehicle composite component to another vehicle element. In particular,the present disclosure refers to an attachment interface for connectinga vehicle suspension upright or knuckle to a steering control arm and/orto support arms of the vehicle suspension.

BACKGROUND OF THE INVENTION

As it is known, e.g. from US2016121927A1, in the interests of fueleconomy there is an increasing drive within the automotive industrytowards weight reduction of the component parts of vehicles. One suchcomponent is the steering knuckle, which connects the wheel bearing tothe vehicle suspension. More in general, such components include all theuprights of the vehicle suspension.

Typically, there is the need of manufacturing the knuckle/upright from alightweight composite material, such as a fiber-reinforced polymer. Inthis field, the most effective composite structure is in the shape of alaminate or plate element, i.e. a relatively thin element that can beformed so as to have suitable curvatures and define a shell portion inthe vehicle component.

However, when choosing composite plate elements for forming vehiclecomponents, a problem arises in how to connect this kind of compositestructure to the other parts of the vehicle and how to transfer alocalized high load to such a composite structure.

Indeed, in the field of vehicle suspension components, the latter areconnected to support or control arms by articulated connections, likeball joints, that transfer very high loads as substantially local(punctual) loads. This can be a limit for the introduction of fiberreinforced polymers in such suspension components, because the compositematerials in the form of plate or shell elements, in general, cannotsustain localized loads.

An example of attachment interface according to the prior art isdisclosed in US2017/008558A1, which corresponds to the preamble of claim1.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide an attachmentinterface for connecting a vehicle composite component, which solves theabove-mentioned problem by ensuring an optimized transfer of forces andloads, to and from such composite component.

According to the invention, an attachment interface for connecting avehicle composite component is provided, as defined in the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The invention will now be described with reference to the accompanyingdrawings, which illustrate a non-limiting embodiment thereof, in which:

FIG. 1 is a perspective view showing a vehicle composite componentprovided with preferred embodiments of the attachment interface,according to the present invention, for connecting such a vehiclecomposite component to other vehicle elements;

FIG. 2 is a cross section of one of the attachment interfaces of FIG. 1,taken along a section plane identified by line II-II in FIG. 1;

FIG. 3 is a cross section of another attachment interface of FIG. 1,taken along a section plane identified by line in FIG. 1;

FIG. 4 is a cross section of another attachment interface of FIG. 1,taken along a section plane identified by line IV-IV in FIG. 1; and

FIGS. 5 and 6 are cross-sections showing respective variants of theattachment interfaces of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, reference number 1 indicates a vehiclelightweight component, defined in particular by a lightweight suspensionupright or knuckle (a steering knuckle in the non-limitative embodimentshown).

The lightweight suspension upright or knuckle 1 is represented in aschematic, non-limitative manner only, in order to make clearer theconcept on which the invention is based. It is therefore clear that thepresent invention applies to vehicle lightweight components having anysuitable different shape and function, so that the invention is notlimited in any manner to the specific embodiment shown.

According to one aspect of the invention, the suspension upright orknuckle 1 is made, in a manner that will be described in details hereinbelow, in a composite material, e.g. a fiber reinforced syntheticplastic resin.

In particular, the suspension upright or steering knuckle 1 comprises abearing connection interface 2 for receiving a wheel rolling bearing 3,the latter being an HBU (Hub Bearing Unit) well known in the art andaccordingly not shown and described in details for sake of simplicity.

The bearing connection interface 2 includes a first sleeve element 4having a cylindrical shape and an axis of symmetry A coinciding, in use,with a rotation and symmetry axis of the wheel bearing 3. In thenon-limiting example shown, the first sleeve element 4 is metallic andpreferably consists of a steel outer ring of the wheel rolling bearingor HBU 3. Alternatively, the first sleeve element 4 may be configured toreceive in known manner, e.g. by interference fitting, the wheel bearing3 and may be, in this case, made either of a metal alloy or of a fiberreinforced synthetic plastic.

According to a preferred aspect of the invention, the bearing connectioninterface 2 also comprises a second sleeve element 5, arranged radiallyoutside the first sleeve element 4, and an annular body 6 arrangedradially inside the second sleeve element 5. The annular body 6 is madeof a composite material, which is preferably selected from the groupconsisting of BMC (Bulk Molding Compound), LFT (Long FiberThermoplastic) and DLFT (Direct Long Fiber Thermoplastic).

In the particular embodiment that is shown, the annular body 6 iscoaxial with the first sleeve element 4.

According to an aspect of the present invention, the lightweightsuspension upright or knuckle 1 comprises a plurality of attachmentinterfaces 9, 9 a, 9 b, 9 c and 9 d, configured to connect, in use, thesuspension upright or knuckle 1 to a respective control or supportelements, known and not shown for sake of simplicity. In particular,attachment interfaces 9 and 9 a are used for the connection of knuckle 1to respective support arms of a vehicle suspension; attachmentinterfaces 9 b and 9 c are used for the connection of a brake caliper toknuckle 1; and attachment interface 9 d is used for the connection ofknuckle 1 to a control or steering arm of a vehicle steering device.

The lightweight suspension upright or knuckle 1 further comprises asupporting structure 11 mechanically connecting the bearing connectioninterface 2 to the attachment interfaces 9,9 a,9 b,9 c,9 d.

The supporting structure 11 is made of a fiber reinforced compositematerial comprising at least one blade or plate element 12. Inparticular, the supporting structure 11 is shaped as a reticular framecomprising a plurality of blade or plate elements 12 chemically and/ormechanically interconnected to each other. Preferably, at least one theblade elements 12 is also chemically and/or mechanically bound directlyto an outer lateral surface of the bearing connection interface 2, so asto join integral in one piece therewith.

Conveniently, each blade element 12 consists in one or more mats orplies of continuous fibers embedded in a polymer matrix. When the bladeelements 12 are formed by more than one mat or plie, the latter arestacked onto one another. In particular, to obtain the blade elements 12such mats or plies have been compression molded to one another and atleast one of the blade elements 12 has been compression molded to theouter surface of the bearing connection interface 2.

More in general, each blade element 12 comprises a (thermoset orthermoplastic) polymer matrix, and reinforcing fibers (e.g. glass and/orcarbon and/or aramid) embedded in such a matrix.

With reference to FIG. 2, according to an aspect of the presentinvention, the attachment interface 9 comprises at least one plate orblade portion, in particular two plate or blade portions 16 and 17,which define part of respective blade elements 12 and are arranged oneover the other.

The plate portion 16 has two opposite faces 18 and 19, with asubstantially constant thickness between faces 18 and 19. According tovariants, not shown, the thickness between faces 18 and 19 is variable.In the specific embodiment that is shown, the plate portion 16 is shapedso as to define a cavity 20, in particular facing towards axis A. Face18 is concave and delimits the cavity 20, while face 19 is convex and isfacing outwards.

In a similar way, the plate portion 17 is defined by two opposite faces23 and 24, preferably with a substantially constant thickness betweenfaces 23 and 24. Face 23 is arranged towards face 19, while face 24 isfacing outwards. In particular, face 23 comprises a zone 25 which isspaced apart from face 19, and a zone 26, which is in contact with azone 27 of face 19 and has a shape matching the one of zone 27.

The plate portions 16 and 17 have respective passages 28 and 29, whichextend through, along an axis 30 transversal to faces 18,19,23,24.

According to an aspect of the present invention, attachment interface 9comprises a composite material 35 that is defined by a fiber reinforcedpolymer, covers at least faces 18 and 24 and, advantageously, isselected from the group consisting of BMC (Bulk Molding Compound), LFT(Long Fiber Thermoplastic) and DLFT (Direct Long Fiber Thermoplastic).

BMC, as well as LFT/DLFT, are synthetic plastic materials in whichindividual reinforcing fibers of considerable length (usually ½ inch or12 mm) are uniformly dispersed within a synthetic plastic matrix withouta specific orientation (or oriented by the flow during the compressionbut never arranged in layers) while, e.g., in SMC materials the fibersare disposed in layers. In BMC materials, the synthetic plastic matrixis generally formed by a thermosetting resin and such materials areadapted to be formed, generally, by compression molding; in LFT/DLFTmaterials the synthetic plastic matrix is defined by a thermoplasticresin and such materials are adapted to be formed byinjection/compression molding.

Moreover, in both the BMC and LFT/DLFT materials the reinforcing fibersare of uniform length.

Preferably, in the final, molded material the individual reinforcingfibers form groups of fibers aligned with respect to each other, and thegroups are uniformly dispersed randomly in the matrix, in order to giverise to a nearly isotropic material.

In particular, composite material 35 is directly in contact with thefaces 18,19,23,24. Composite material 35 comprises at least two layers36,37 respectively arranged in fixed positions on plate portions 16, 17and axially delimited, respectively, by surfaces 38 and 39, opposite toeach other along axis 30. In such a way, the plate portions 16 and 17are sandwiched between the layers 36 and 37. In particular, layers 36and 37 are defined by pieces that are separate from one another.

Conveniently, the composite material 35 comprises a further layer 40,which fills in any possible gap between faces 23 and 19 and, inparticular, is integral with layer 36, so as to define a single pad orblock, that encloses at least part of the plate portion 17 (FIG. 1). Onthe other side, layer 37 defines a pad that fills in, at least partly,the cavity 20.

The attachment interface 9 further comprises an attachment device 41made of metal material (e.g. aluminum alloy and/or steel) and comprisingan insert 42, which engages passages 28 and 29 and is at least partlyembedded in the composite material 35. In the shown embodiment, insert42 comprises a sleeve 43, which coaxially engages passages 28 and 29, isembedded in the composite material 35 and has an axial hole 44,preferably open at both axial ends of the sleeve 43, such axial endsbeing indicated by reference numbers 45 and 46.

Preferably, the insert 42 further comprises a flange 48, which isprovided at the axial end 45, projects radially outwardly from thesleeve 43 and defines an annular shoulder 49 extending transversally toaxis 30 and in contact with surface 38. In the particular non limitingexample, flange 48 is partially embedded in layer 36.

Preferably, the metal attachment device 41 further comprises a washer53, which is spaced apart from insert 42 (i.e. is spaced apart from theaxial end 46 of the sleeve 43) and defines a shoulder 54 extendingtransversally to axis 30 and in contact with surface 39. Morepreferably, washer 53 is partially embedded in layer 37.

In this way, the composite material 35 is axially sandwiched between theshoulders 49 and 54. In order to obtain this arrangement during themanufacturing process, conveniently, the composite material 35 is castin a molding process so as to be shaped according the profile of thefaces 18,19,23,24. In other words, the insert 42 and the washer 53 arefirst placed in a mold, along with the plate elements 12; afterwards, afiber reinforced polymer, e.g. a BMC compound, is overmolded onto theplate portions 16 and 17, the insert 42 and the washer 53 so as to fillin the void spaces; and finally such polymeric material is cured tofinally form the layers of the composite material 35.

According to a variant, the insert 42 and/or the washer 53 are providedafter having overmolded the fiber reinforced polymer onto the plateportions 16 and 17, i.e. the insert 42 and/or the washer 53 are coupledto the composite material 35 already formed by molding.

Still with reference with FIG. 2, the metal attachment device 41 furthercomprises an attachment element 55, which has a shape elongated alongaxis 30 and, in turn, comprises a pin inner portion 56, coaxiallyengaging the hole 44, and an attachment outer portion 57, axiallyprojecting outside of the composite material 35 and the insert 42 so asto define a connection point for connecting another vehicle component.In the attachment interface 9 shown in FIG. 2, the attachment outerportion 57 comprises a spherical joint 58 suitable to be coupled to asuspension arm (not shown).

The attachment element 55 is coupled in a fixed position to the insert42 thanks to a coupling, preferably a threaded coupling comprising athreaded end portion 60 of the attachment element 55 and a threaded nut61, which is screwed on portion 60 and axially rests (directly orindirectly) on washer 53. In the meantime, the pin inner portion 56 isaxially hold in the hole 44 in a fixed position by a conic fitting. Inother words, the pin inner portion 56 has a conical surface 63 which isin contact and matches with a conical surface 64 of the sleeve 43 at theaxial end 45. It is evident that the tightening exerted on the threadedcoupling causes an axial tension on the pin inner portion 56 and aconsequent axial compression on the composite material 35 between theshoulders 49 and 54. Indeed, the axial load exerted by the tightenedthreaded coupling is transferred by the conical surface 63 on theconical surface 64 and, therefore, on the whole insert 42; thanks tothis axial load, the flange 48 is axially pulled towards the washer 53so as to compress the composite material 35 and, therefore, the plateportions 16 and 17 along axis 30.

According to variants that are not shown, the conic fitting can bereplaced by a flange of the portion 57, axially resting onto the flange48, or directly onto the surface 38 (i.e. without a flange at the axialend 45).

The use of the composite material 35 to form layers 36, 37 and 40, inwhich the plate portions 16 and 17 are sandwiched, allows fortransferring and distributing loads between the metal attachment device41 and the plate portions 16,17 in a more uniform manner. Indeed, theloads are not transferred directly between the sleeve 43 of the insert42 and the plate portions 16,17 (at the edge of the passages 28,29), butthey are transferred between the insert 42 and the composite material35, on the one hand, and between the composite material 35 and the faces18,19,23,24, on the other hand. In other words, the layers 36, 37 and 40have the function of progressively distributing a localized load alongthe relatively wide areas of the faces 18,19,23,24, so as to obtainlower localized stresses on the plate portions 16,17 that are covered bysuch layers 36, 37 and 40. In particular, the insert 42 receives theload from the attachment element 55 by the threaded coupling andtransfers such load to the composite material 35, that is formed so todistribute (preferably in an uniform manner) the load to the wider areasof the plate portions 16,17 without exceeding the allowed stresses. Inother words, during the design stage the parts of the attachmentinterface 9 are to be sized so as to achieve in each transition acontact pressure that, in any loading condition resulting from thespecific case, is not exceeding the stresses allowed by the specificmaterial.

As mentioned above, the attachment interface 9 is also made to keep theplate portions 16 and 17 compressed, in direction parallel to axis 30,between shoulders 49 and 54: this compression aids in preventingpossible delamination failures of the plate portions 16 and 17. Theapplied pre-compression has to be high enough to keep the plate portions16,17 in a compression state, but without exceeding compression limits.

FIG. 3 shows the attachment interface 9 a, which comprises partsindicated by the same reference numbers used in FIG. 2 for theattachment interface 9, but followed by reference letter “a”. Incomparison with the metal attachment device 41 of FIG. 2, the metalattachment device 41 a has an arrangement that is inverted so as toprovide the spherical joint 58 a in the cavity 20 a and provide thewasher 53 a on the surface 38 a.

Besides, conveniently, the layer 36 a comprises a peripheral portion 65,having a substantially constant thickness with respect to face 24 a, andan intermediate portion 66 housing the axial end 46 a and having ahigher thickness than the peripheral portion 65.

FIG. 4 shows the attachment interface 9 b, which comprises partsindicated by the same reference numbers used in FIG. 2 for theattachment interface 9, but followed by reference letter “b”.

In comparison with the attachment interface 9 of FIG. 2, the attachmentinterface 9 b comprises only one plate portion 16 b sandwiched betweenlayers 36 b and 37 b. In particular, layer 36 b is arranged directly onface 19 b. Besides, preferably, the flange 48 b is provided in thecavity 20 b, in contact with surface 39 b. On the other axial side, inthe specific embodiment that is shown, the metal attachment device 41 bdoes not comprise any washer. More specifically, end 46 b of the sleeve43 b is not completely embedded in the composite material 35 and, inparticular, is flush with surface 38 b.

In this embodiment, preferably, the attachment element 55 b is definedby a screw or bolt, comprising a stem having a threaded inner portion 56b screwed into the axial hole 44 b. The attachment element 55 b has anouter portion 57 b defining a connection point for another vehicleelement, e.g. for connecting a brake caliper (not shown). In particular,the outer portion 57 b of the attachment element 55 b comprises an endportion or head 58 b suitable to axially clamp the vehicle element to beconnected, between the surface 38 b and an annular shoulder 54 b of thehead 58 b. This axial clamping action can also exert an axialcompression of the composite material 35 b between the vehicle elementto be connected and the shoulder 49 b of the flange 48 b.

The attachment interface 9 c is identical to attachment interface 9 b,and therefore is not described for sake of simplicity.

According to variants that are not shown, the head 58 b can be replacedby a nut, screwed onto a threaded end of the outer portion 57 b, and/orthe latter could be integral with the insert 42 b (i.e. the attachmentelement 55 b and the insert 42 b are replaced by a single metal piece,comprising an inner portion, embedded in the composite material, and aprojecting outer portion defining a connection point for the vehicleelement to be connected).

FIG. 5 partially shows a variant providing two plate portions 16 c and17 c that are substantially planar (instead of being curve and/ordefining a cavity). Besides, conveniently, the plate portions 16 c and17 c are interposed between composite layers 36 c, 37 c and 40 c, whichare integral with each other, i.e. they define parts of a single body ofcomposite material 35 c (having the features of composite materials35,35 a,35 b). Preferably, but not necessarily, the plate portions 16 cand 17 c are completely spaced apart from each other. According to thisvariant, in particular, a metal attachment device 41 c (partially shown)is provided with an insert 42 c having a relatively thick flange 48 c.

FIG. 6 partially shows a variant of the attachment device, indicated byreference numeral 41 d. The metal attachment device 41 d comprises aninsert 42 d, which is defined by a sleeve or bushing, without anyflange. In particular, this arrangement is used when there is no need ofaxially compressing the plate portion 16 d between the layers of thecomposite material 35 d. According to another variant that is not shown,the insert 42 d is absent and the metal attachment device 41 d comprisesa bolt, which has an inner portion extending through the axial passagesin the plate portion 16 d and in the layers of the composite material 35d, and an outer portion suitable to connect another vehicle element. Inthe meantime, the bolt can be fastened by a nut to compress thecomposite material 35 d, e.g. between two washers.

It should be evident that in all the embodiments and variants that havebeen described above, the composite material selected from the groupconsisting of BMC, LFT and DLFT defines layers in which the compositeplate portions are sandwiched to distribute the loads transferred by themetal attachment device 41,41 a,41 b,41 c,41 d to such plate portions.Besides, preferably, the composite material selected from the groupconsisting of BMC, LFT and DLFT is sandwiched to compress the plateportions and prevent possible delamination thereof.

Therefore, the attachment interface according to the present inventiondefines a more effective way of using composite materials in complex andheavily loaded applications, such as car corner suspensions. In themeantime, attachment interface according to the present invention isrelatively flexible, as it can be used with metal attachment deviceshaving different arrangements and/or different configurations. Inparticular, the use of a threaded coupling in the metal attachmentdevice 41,41 a,41 b,41 c,41 d allows for easily compressing the plateportions between the layers of the composite material 35,35 a,35 b,35c,35 d.

Furthermore, it is clear that the attachment interface of the presentinvention is relatively simple and economic to be manufactured, inaddition to being performant. In particular, the layers of the compositematerial 35,35 a,35 b,35 c,35 d may be shaped according to the designrequirements, in a simple manner.

All the objects of the invention are therefore achieved.

Finally, it should be evident that the attachment interface of thepresent invention can be applied to vehicle components different fromthe suspension uptight/knuckle 1 that has been shown as a particularnon-limiting example.

What is claimed is:
 1. An attachment interface for connecting a vehiclecomposite component, the attachment interface comprising: a first plateportion that is part of the composite component, is made of a firstfiber reinforced polymer composite material and has a first passageextending in a through manner along an axis; a metal attachment devicethat comprises an inner portion engaging the first passage and an outerportion defining a connection suitable to be connected to anothervehicle element; wherein the first plate portion is axially sandwichedbetween two layers made of a second fiber reinforced polymer compositematerial; and a second plate portion, arranged between the first plateportion and one of the layers and having a second passage, which iscoaxial with the first passage and is engaged by the inner portion. 2.The attachment interface according to claim 1, wherein the second fiberreinforced polymer composite material is selected from the groupconsisting of BMC (Bulk Molding Compound), LFT (Long FiberThermoplastic) and DLFT (Direct Long Fiber Thermoplastic).
 3. Theattachment interface according to claim 1, wherein the inner portion isat least partly embedded in the second fiber reinforced polymercomposite material.
 4. The attachment interface according to claim 3,wherein the inner portion is an insert comprising a sleeve that has anaxial hole; the outer portion being part of an attachment elementengaging the axial hole in a fixed position.
 5. The attachment interfaceaccording to claim 1, wherein the first and second layers are directlyin contact with the first plate portion.
 6. The attachment interfaceaccording to claim 1, wherein the metal attachment device comprises: afirst and a second shoulder transverse to the axis; the second fiberreinforced polymer composite material being axially sandwiched betweenthe first and the second shoulder; and a coupling suitable to betightened so as to axially compress the second fiber reinforced polymercomposite material between the first and second shoulders.
 7. Theattachment interface according to claim 6, wherein the first shoulder isdefined by a washer.
 8. The attachment interface according to claim 6,wherein the inner portion is an insert comprising a sleeve, and thesecond shoulder is defined by a flange provided at an axial end of thesleeve.